One trait in the philosopher's character we can assume is his love of the knowledge that reveals eternal reality, the realm unaffected by change and decay. He is in love with the whole of that reality, and will not willingly be deprived even of the most insignificant fragment of it - just like the lovers and men of ambition we described earlier on.
Consider how great is the encouragement which all the world gives to the lover; neither is he supposed to be doing anything dishonourable; but if he succeeds he is praised, and if he fail he is blamed.
A sensible man will remember that the eyes may be confused in two ways - by a change from light to darkness or from darkness to light; and he will recognize that the same thing happens to the soul.